the trouble with antiques

The Space Shuttle is an antique. The design is pure 1970s, down to the rad-hard Z80 processors in its main computer. To get software to fit into a Z80 you have to jettison every possible bell and whistle. In particular, the Shuttle's software is so dumb that it was immune to Y2K bugs, because there wasn't room to store the year in the date representation.

Handy, but this has a side-effect: the Shuttle can't be on orbit at New Years.

There's a workaround for emergency missions, but the point here is that like an antique car, the Shuttle is not a rainy-day vehicle, and trying to turn it into one is hopeless.